Semiconductor light emitting device

ABSTRACT

A semiconductor laminating portion including a light emitting layer forming portion having at least an n-type layer and a p-type layer is formed on a semiconductor substrate. A current blocking layer is partially formed on its surface. A current diffusing electrode is formed on the entire surface thereof. A bonding electrode is formed thereon. The semiconductor laminating portion and the current diffusing electrode are separated into light emitting unit portions A, electrode pad portion B, and connecting portions C for connecting between electrode pad portion B and light emitting unit portions A or between two of the light emitting unit portions A, and the semiconductor laminating portion between the light emitting unit portions A is removed through etching to make clearances except for connecting portions C. The bonding electrode is formed on electrode pad portion B.

FIELD OF THE INVENTION

The present invention relates to a semiconductor light emitting devicearranged in that it is capable of extracting light, which is emittedfrom a light emitting layer forming portion in which a light emittinglayer is formed by laminating semiconductor layers, to the utmost from alight emitting device chip (hereinafter also referred to as “LED chip”)and of improving the luminance with respect to the same amount of input.More particularly, it relates to a light emitting device arranged inthat light is effectively extracted from side surfaces of light emittingportions so as to achieve improvements in light extraction efficiency ofemitted light to the exterior.

BACKGROUND OF THE INVENTION

A conventional type visible light semiconductor light emitting deviceemploying, for instance, In_(0.49) (Ga_(1-z)Al_(z))_(0.51)P basedcompound semiconductor may be arranged as exemplarily illustrated inFIG. 4. That is, FIG. 4 illustrates a light emitting layer formingportion 29 of double hetero structure in which there are deposited, on asemiconductor substrate 21 of n-type GaAs, an n-type clad layer 22 madeof a n-type InGaAlP based semiconductor material, an active layer 23made of a InGaAlP based semiconductor material having a composition withwhich the band gap energy becomes smaller than that of the clad layers,and a p-type clad layer 24 of a p-type InGaAlP based semiconductormaterial, respectively, through epitaxial growing. A p-type window layer(current diffusing layer) 25 made of an AlGaAs based compoundsemiconductor is further deposited on a surface thereof. Moreover, ap-side electrode 27 is formed on a central portion of this surface witha contact layer 26 of GaAs being interposed between them while an n-sideelectrode 28 is formed on a rear surface of the semiconductor substrate.

The window layer 25 is employed for the purpose of achieving twofunctions, namely enabling easy extraction of light from side surfacesand enabling easy light emission at the light emitting layer formingportion on the entire surface of the chip by diffusing current forspreading the same over the entire surface of the chip, and it is formedby a semiconductor layer of small light absorption rate and largecarrier density.

In such a semiconductor light emitting device, light directed towardsthe p-side electrode 27 that is provided on the surface side will beshielded by this electrode 27 so that no light can be extracted to thesurface side. For eliminating such loss, it is known to provide anarrangement in which a semiconductor layer of different conductivityfrom the conductivity of the adjoining semiconductor layers or aninsulating layer is interposed between any of the semiconductor layers,which is underlying the p-side electrode 27 as indicated by 31 in FIG. 5so as to restrict current to directly underneath the p-side electrode 27and thus to avoid emitting light directly underneath thereof.

As already discussed, in a conventional semiconductor light emittingdevice in which light is extracted from a surface side of laminatedsemiconductor layers, light emitted in the interior cannot besufficiently extracted since light is shielded by an electrode that isprovided on the surface side. Such an electrode on the surface siderequires a bonding area of approximately 80 to 100 μmφ for wire bondingor the like, in a size of the chip area of approximately 200 to 300 μmsquare, which leads to a drawback in that most of the area is shieldedby the electrode so as to degrade the efficiency of extraction of lightto the exterior.

Further, even though current is prevent from flowing by providing acurrent blocking layer downward of the upper electrode (p-sideelectrode) as illustrated in the above-mentioned FIG. 5, current willstill flow to the active layer portion further downward thereof to causeemission of light, and even if emission of light has been successivelybeen prevented, light emitted in the periphery thereof will be absorbedby the active layer, which is a portion that does not emit light, sothat portions that emit light downward of the upper electrode cannot beeffectively used.

Moreover, when trying to extract light from side wall of the chip, theside wall will only be the periphery of the rectangular chip while thelight emitting region is, in the presence of a region in which currentinjection is blocked, substantially the entire surface of the chip areaof the active layer that is formed to be vertical with respect to theside wall excluding the above blocking region, and light emitted in theinterior such as the central portion of the chip cannot be effectivelyextracted to the exterior owing to factors such as absorption by thesemiconductor layers.

SUMMARY OF THE INVENTION

The present invention has been made for solving such problems, and it isan object thereof to provide a semiconductor light emitting device of anarrangement with which light emitted in a light emitting layer formingportion can be effectively extracted to the exterior for improving theluminance with respect to input.

The semiconductor light emitting device according to the presentinvention includes; a semiconductor substrate, a semiconductorlaminating portion formed on the semiconductor substrate, which includesa light emitting layer forming portion having at least an n-type layerand a p-type layer, a current diffusing electrode formed on thesemiconductor laminating portion, which exhibits translucency andelectric conductivity, a bonding electrode formed on a part of thecurrent diffusing electrode, and an electrode formed on a rear surfaceof the semiconductor substrate, wherein the semiconductor laminatingportion and the current diffusing electrode are separated into aplurality of light emitting unit portions, an electrode pad portion, andconnecting portions for connecting between the electrode pad portion andthe light emitting unit portions or between two of the light emittingunit portions, and wherein the bonding electrode is provided on theelectrode pad portion, and the electrode pad portion is formed so as tomake the light emitting layer forming portion in the electrode padportion nonluminous.

For forming the current diffusing electrode, it is possible to form analloy layer of Au—Ge or Au—Ni to have a thickness of approximately 2 to200 nm or to utilize an ITO layer. For making the light emitting layerforming portion nonluminous, it is possible to insert a current blockinglayer such as an insulating layer or a semiconductor layer having aconductivity that is different from the conductivity of the adjoiningsemiconductor layers, between the current diffusing electrode and theelectrode on the rear surface of the semiconductor substrate.

It is preferable that the size of the light emitting units portions isformed such that its diameter, when it is of circular planar shape, orits longer side or its longer diameter, when it is of rectangular orelliptic shape, is not more than six times of the height of thesemiconductor laminating portion since also light emitted in the centralportion may be extracted to the exterior. By setting a distance betweenadjoining two of a plurality of light emitting unit portions to be notless than twice of the height of the semiconductor laminating portion,extracted light may be utilized without any mutual interference andcancellation so that the luminance may be improved.

With this arrangement, the light emitting unit portions and theelectrode pad portion are formed to be separate from each other whilethe electrode pad portion is also formed to be nonluminous, neither willcurrent be wasted nor will light emitted at the light emitting unitportions be absorbed by nonluminous portions such as the electrode padportion; moreover, since light emitting unit portions are providedseparately by a plurality of numbers, light emitted at the respectivelight emitting unit portions will not cancel each other in lateraldirections but may be easily extracted immediately from the side wallsfor effective utilization thereof. It is consequently possible toextremely improve the luminance of light that may be effectivelyutilized and thus to remarkably improve efficiency of light emission.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1A and FIG. 1B are a perspective and a sectional explanatory viewof an LED chip illustrating one embodiment of the present invention;

FIGS. 2A and 2B are views for explaining a suitable example of size anddistance between two of the light emitting unit portions as illustratedin FIG. 1;

FIGS. 3A to 3D are explanatory views illustrating processes formanufacturing the LED chip as illustrated in FIG. 1;

FIG. 4 is a sectional explanatory view illustrating a exemplar structureof a conventional LED chip; and

FIG. 5 is a sectional explanatory view illustrating an exemplarstructure of a conventional LED chip.

DETAILED DESCRIPTION

A semiconductor light emitting device according to the present inventionwill now be explained while referring to the drawings. The semiconductorlight emitting device according to the invention is arranged, asexplanatory illustrated in FIGS. 1A and 1B as a schematic perspectiveview of one embodiment thereof and as an explanatory view seen fromsection B-B in FIG. 1A, in that a semiconductor laminating portion 12including a light emitting layer forming portion 11 having at least ann-type layer 2 and a p-type layer 4 is formed on a semiconductorsubstrate 1. On the semiconductor laminating portion 12, there areprovided a current blocking layer 7 in a partial portion and a currentdiffusing electrode 8 on the entire surface thereof that exhibitstranslucency and electric conductivity. A bonding electrode 9, which isone electrode of a pair of electrodes, is formed on a part of thecurrent diffusing electrode 8 and the other electrode 10 is provided onthe rear surface of the semiconductor substrate, respectively.

The above semiconductor laminating portion 12 and the current diffusingelectrode 8 are separated into a plurality of light emitting unitportions A, an electrode pad portion B and connecting portions C forconnecting between the electrode pad B and the light emitting unitportions A or between two of the light emitting unit portions A, whereinclearance portions between the respective light emitting unit portions Aare formed by removing the semiconductor laminating portion 12 exceptfor the connecting portions C through etching so that the respectivelight emitting unit portions A and the electrode pad portion B projectin a piled manner while each of them is connected by the connectingportion C as illustrated in FIG. 1A. The above-described bondingelectrode 9 is formed on the electrode pad portion B and the currentblocking layer 7 is provided only in the electrode pad portion B and theconnecting portions C so that current can be blocked from flowing to theunderlying light emitting layer forming portion 11 so that this portionsis nonluminous region.

Namely, other portions than the light emitting unit portions A areprovided with a current blocking layer 7 such that current is injectedto the light emitting unit portions A only, and the light emitting unitportions A are provided upon being separated into a plurality ofnumbers. Since the current diffusing electrode 8 is provided on thesurface of the light emitting unit portions A so that current may bediffused while permitting light to pass through, light emitted at thelight emitting unit portions A may be extracted not only from theirupper surface sides but also from their side walls. On the other hand,while no light may pass through the electrode pad portion B since thebonding electrode 9 is formed on the surfaces of the electrode padportion B, no current will be injected to the light emitting layerforming portion 11 in the electrode pad portion B to cause no lightemission since the electrode pad portion B is provided with the currentblocking layer 7.

The connecting portions C are for transmitting an electric potentialthat is applied to the bonding electrode 9 to the respective lightemitting unit portions A, and in the example as illustrated in FIGS. 1Aand 1B, the connecting portions C are also formed with the currentblocking layer 7 so that no light is emitted at the connecting portionsC as well. When the connecting portions C are also arranged to benonluminous, their surfaces may be formed with the same metallicelectrode as the bonding electrode; alternatively, when using thecurrent diffusing electrode 8 only, the connecting portions C may alsofunction as light emitting regions by omitting the current blockinglayer 7.

The relationship between light emitting unit portions A, the electrodepad portion B and the connecting portions C may be defined such that xand z in FIG. 1A satisfy the following relationship (note that FIG. 1 isa schematic view wherein the relationship of size is not necessarilyaccurate, and that the semiconductor laminating portion 12 of FIG. 1B isillustrated in thickened form). More particularly, it is preferable thatthe size (diameter x) of each of the light emitting unit portions A isnot too large for enabling extraction of light emitted in the interiorthereof not only from their surfaces but also from their side walls. Theinventors of the present invention studied hard to find out, uponvariously changing the thickness z of the semiconductor laminatingportion 12 and the diameter x of the light emitting unit portions A (seeFIG. 2A), that light can be effectively extracted by setting the size ofthe thickness z of the semiconductor laminating portion 12 and thediameter x such that z≧x/6 is satisfied. The thickness z of thesemiconductor laminating portion 12 may be formed to be approximately 3to 10 μm whereas the diameter of each of the light emitting unitportions A is formed to be approximately to 10 to 50 μm.

In other words, the inventors have found out that the above-mentionedspecified relationship holds between the thickness z and the diameter xof each of the light emitting unit portions A, wherein while lightemitted at the light emitting portions A can be easily extracted to theexterior even when the planar area of the light emitting unit portions Ais large, provided that the thickness z of the semiconductor laminatingportion 12 is large, it will become difficult to extract light emittedin the central portions of the light emitting unit portions A when thethickness of the semiconductor laminating portion 12 is small.

The planar shape of each of the light emitting layer unit portions A isnot limited to the circular shape as illustrated in FIG. 1. A circularplanar shape is preferable since light irradiated in every directionfrom the central portion will be directed substantially vertical to theside walls regardless of their direction of propagation so that theangle of incidence may be made small to thereby enable easy extractionto the exterior. However, since light is emitted at every portion of theactive layer 4 of the light emitting unit portions A and moreover, sincesuch light will propagate in every direction not only within a planarplane but also in vertical directions, the planar shape is not limitedto a circular one but may alternatively be rectangular, square orelliptical, resulting in no particular differences. In this case, lightcan be effectively extracted when a relationship substantially identicalto the above-described relationship between the thickness z of thesemiconductor laminating portion and the size is satisfied, wherein thedimension of the longer side or the dimension of the diagonal line isemployed as the value of the above x.

Further, when the clearance between adjoining two of the light emittingunit portions A is too small, light extracted from one light emittingunit portion A will interfere with light extracted from an adjoininglight emitting unit portion A to be cancelled, and it is thus necessaryto provide a specified distance. The inventors of the present inventionperformed tests upon variously changing the distance y between two ofthe light emitting unit portions A as illustrated in FIG. 2B to find outthat this distance y is also closely related to the thickness z of thesemiconductor laminating portion 12 and that light could be effectivelyextracted by satisfying y≧2z.

The wire bonding electrode 9 is provided on the surface of the currentdiffusing electrode 8 of the electrode pad portion B. More particularly,a conventional semiconductor light emitting device exhibited a drawbackthat an electrode for connection with a power source for supplyingvoltage needed to be provided on both, upper and lower surfaces of thelight emitting device chip wherein no light was allowed to pass throughthe wire bonding electrode 9 so that light emitted downward thereofcould not be effectively utilized. A great loss was also caused sincethe portion of the bonding electrode 9 occupied quite a large area of,for instance, approximately 80 to 100 μmφ with respect to a chip size ofapproximately 330 μm square.

The present invention has thus been arranged in that a portion forforming the bonding electrode 9 thereon is separated from the lightemitting unit portions A as electrode pad portion B and in that thecurrent blocking layer 7 is formed in the electrode pad portion B sothat current is completely prevented from flowing. It has consequentlybeen enabled to eliminate losses in which light is not emitted by notbeing injected current to the light emitting layer forming portion underthe bonding electrode, and further to remarkably reduce a ratio ofabsorption of light, which emits from the light emitting unit portions Aadjoining to the electrode pad portion B and enters into the activelayer of the electrode pad portion B.

The connecting portions C are provided for transmitting voltage of anexternal power source applied to the bonding electrode 9 to therespective light emitting unit portions A via the current diffusingelectrode 8. In the example illustrated in FIG. 1, the current blockinglayer 7 is provided in the connecting portions C so that no current ismade to flow for preventing emission of light. However, it is possibleto alternatively employ an arrangement in which the connecting portionsC are also arranged to emit light with no current blocking layer 7 beingprovided in the connecting portions C.

When the connecting portions C are not arranged to emit light, the samemetallic electrode as the bonding electrode 9 may be formed on thecurrent diffusing electrode 8. When not particularly arranged to emitlight, the connecting portions C shall simply conduct voltage to therespective light emitting unit portions A with little loss byresistance, and the smaller the width thereof is, the better it is.Though depending on the fact whether a metallic electrode film (the samemetallic film as the bonding electrode 9) is provided or not, hardly anyohmic dissipation will be generated for allowing current to flow throughwith a width of approximately 5 to 20 μm. When the connecting portions Care also to emit light, the width shall be set to be not more than theabove-mentioned value for x.

As for the semiconductor substrate 1, while GaAs is generally employedfor growing a semiconductor laminating portion of AlGaAs basedsemiconductor or InGaAlP based semiconductor, the substrate may also beof a material such as GaP permitting transmission of light. Thesemiconductor substrate 1 may be either of p-type or n-type, dependingon the relationship with the semiconductor laminating portion 12 that isto grow on the semiconductor substrate 1.

In the example as illustrated in FIG. 1, the light emitting layerforming portion 11 is arranged as a double hetero structure in which theactive layer 3 is sandwiched between the n-type clad layer 2 and thep-type clad layer 4 made of a material having a larger band gap thanthat of the active layer 3, wherein InGaAlP based semiconductor ismainly used for obtaining red light and AlGaAs based semiconductor forinfrared light. For growing the light emitting layer forming portion 11,a required composition and a required thickness is selected depending onthe desired emission wavelength for the device (i.e. changing acomposition ratio of Al or doping a dopant).

Here, an InGaAlP based semiconductor is expressed in the form ofIn_(0.49)(Ga_(1-u)Al_(u))_(0.51)P and indicates a material in which thevalue of u is variously changed in the range of 0 to 1. The mixedcrystal ratio 0.49 and 0.51 between In and (Al_(u)—Ga_(1-u)) indicates aratio of lattice matching between the InGaAlP based semiconductor thatis to be laminated and the semiconductor substrate of GaAs or similar,and an AlGaAs based semiconductor is expressed in the form ofAl_(v)Ga_(1-v)As and indicates a material in which the value of v isvariously changed in the range of 0 to 1.

In one concrete example in which the element is made of, for instance,an InGaAlP based compound semiconductor, it is formed as a laminatedstructure including an n-type clad layer 2 of Se-dopedIn_(0.49)(Ga_(0.25)Al_(0.75))_(0.51)P and having a carrier density ofapproximately 1×10¹⁷ to 1×10¹⁹ cm⁻³ and a thickness of approximately 0.1to 2 μm, an active layer 3 of undopedIn_(0.49)(Ga_(0.8)Al_(0.2))_(0.51)P and having a thickness ofapproximately 0.1 to 2 μm, and a p-type clad layer 4 of Zn-doped InGaAlPbased compound semiconductor having a composition that is identical tothat of the n-type clad layer 2 and having a carrier density ofapproximately 1×10¹⁶ to 1×10¹⁹ cm⁻³ and a thickness of approximately 0.1to 2 μm.

Alternatively, when the device is comprised of AlGaAs based compoundsemiconductor, it is formed as a laminated structure including an n-typeclad layer 2 of Se-doped Al_(0.7)Ga_(0.3)As and having a carrier densityof approximately 1×10¹⁷ to 1×10¹⁹ cm⁻³ and a thickness of approximately0.1 to 2 μm, an active layer 3 of undoped Al_(0.2)Ga_(0.8)As and havinga thickness of approximately 0.1 to 2 μm, and a p-type clad layer 4 ofZn-doped AlGaAs based compound semiconductor having a composition thatis identical to that of the n-type clad layer 2 and having a carrierdensity of approximately 1×10¹⁶ to 1×10¹⁹ cm⁻³ and a thickness ofapproximately 0.1 to 2 μm.

A window layer 5 of, for instance, p-type Al_(w)Ga_(1-w)As (0.5≦w≦0.8)is then formed onto the p-type clad layer 4 of the light emitting layerforming portion 11 by approximately 1 to 10 μm to comprise asemiconductor laminating portion 12 together with the above lightemitting layer forming portion 11.

In the electrode pad portion B and the connecting portions C, a currentblocking layer 7 is provided on the semiconductor laminating portion 12.The current blocking layer 7 may be formed as an insulating layer suchas SiO₂ or as a semiconductor layer having a conductivity that isdifferent from that of the adjoining semiconductor layers such as ann-type AlGaAs based compound semiconductor layer on the p-type windowlayer 5, and is formed to have a thickness of approximately 0.1 to 0.4m. While the current blocking layer 7 is not formed in the lightemitting unit portions A, it is also possible to refrain from formingthis layer in the connecting portions C as well so as to make theconnecting portions C emit light.

The current diffusing electrode 8 is formed as a layer that makescurrent flow between the bonding electrode 9 and the respective lightemitting unit portions A while further allowing light pass through suchthat light emitted in the active layer 3 of the light emitting unitportions A may be extracted to the surface side without being shielded.As for the current diffusing electrode 8, an alloy layer such as Au—Geor Au—Ni is formed to have a thickness of approximately 2 to 100 nm, andmore preferably to be not more than approximately 10 nm. It is alsopossible to employ an ITO film as the current diffusing electrode 8. Thecurrent diffusing electrode 8 is provided over substantially the entiresurface, regardless of the presence or absence of the current blockinglayer 7. However, portions at which the light emitting unit portions Aare separated are removed together with the semiconductor laminatingportion 12.

The chip is formed by respectively forming a bonding electrode (p-sideelectrode) 9 of Au—Be/Ni/Ti/Au or similar on the surface side of thecurrent diffusing electrode 8 on the electrode pad portion B while theother electrode (n-side electrode) of Au—Ge/Ni/Au or similar is formedon the rear surface of the semiconductor substrate 1.

Though not shown in the example of FIG. 1, it is also possible to inserta reflecting layer (DBR; Distributed Brag Reflector) in whichsemiconductor layers of different refractive indices are alternatelylaminated by layers of 5 to 40 to be of a thickness of λ/(4n)(wherein λindicates a light emitting wavelength and n a refractive index of thesemiconductor layer), and a buffer layer between the n-type clad layer 2and the semiconductor substrate 1. It is possible to form an n-typewindow layer to be of the same composition as the window layer 5 also ona semiconductor substrate side surface of the n-type clad layer 2.

The reflecting layer (DBR) may be obtained by a layer that has a bandgap that is larger than that of the active layer or the substrate, forinstance, by a laminated structure in which the composition of Al ofAlGaAs based semiconductor has been changed. The buffer layer may be alayer that is made of the same material as that of the semiconductorsubstrate 1 or a layer with which lattice mismatching between thesemiconductor substrate 1 and the semiconductor layers on thesemiconductor substrate can be eased; for instance, where thesemiconductor laminating portion 12 is of InGaAlP based compound and thesemiconductor substrate 1 is of GaAs, GaAs, InGaP or InGaAlP basedcompound may be used, and where the semiconductor laminating portion 12is of AlGaAs based compound and the semiconductor substrate 1 is ofGaAs, GaAs or AlGaAs based compound may be used.

For manufacturing such an LED chip, it is possible to put an n-type GaAssubstrate 1 into a MOCVD (metal organic chemical vapor deposition)apparatus, and to introduce required gases for growth together with acarrier gas of hydrogen (H₂), of reaction gases such as triethylgallium(hereinafter referred to as TEG), trimethylaluminum (hereinafterreferred to as TMA), trimethylindium (hereinafter referred to as TMIn)and phosphin (hereinafter referred to as PH₃) and H₂Se as an n-typedopant gas.

First, as illustrated in FIG. 3A, epitaxial growth is performed at 500to 700° C. to obtain an n-type clad layer 2 ofIn_(0.49)(Ga_(0.25)Al_(0.75))_(0.51)P having a carrier density ofapproximately 1×10¹⁶ to 1×10¹⁹ cm⁻³ by approximately 0.5 μm on thesurface of the semiconductor substrate 1. Then, the amount of thereaction gas TMA is reduced to increase the amount of TEG for forming anactive layer 3 of undoped In_(0.49) (Ga_(0.8)Al_(0.2))_(0.51)P byapproximately 0.5 μm, and the dopant gas is changed to dimethyl zinc(DMZn) by using the same reaction gas as the n-type clad layer 12 forforming a p-type clad layer 4 of p-typeIn_(0.49)(Ga_(0.25)Al_(0.75))_(0.51)P having a carrier density ofapproximately 1×10¹⁷ to 1×10¹⁹ cm⁻³ by approximately 1 μm and a p-typewindow layer 5 of p-type Al_(0.7)Ga_(0.3)As having a carrier density ofapproximately 1×10¹⁷ to 1×10²⁰ cm⁻³ to thereby obtain the semiconductorlaminating portion 12.

Then, as illustrated in FIG. 3B, an SiO₂ layer 7 a is formed on thesurface thereof through, for instance, CVD method, to assume a thicknessof approximately 0.02 to 0.4 μm. Then, a resist film (not shown) isformed on the surface thereof to perform patterning throughphotolithographic techniques such that the resist film remains only onthe electrode pad portion B and the connecting portions C whereupon theremaining resist film is used as a mask for performing etching of theSiO₂ layer 7 a using hydrofluoric acid and for accordingly forming thecurrent blocking layer 7 only on the surface of the electrode padportion B and the connecting portions C.

Thereafter, as illustrated in FIG. 3D, Ni and Au are deposited onto theentire surface and carried on sintering so that the current diffusingelectrode 8 of Au—Ni alloy is formed to assume a thickness ofapproximately 10 nm. A resist film is formed on the electrode padportion B on the surface thereof such that the bonding electrode 9 maybe formed, and the bonding electrode (p-side electrode) 9 ofAu—Be/Ni/Ti/Au or similar is formed through lift-off to have a thicknessof approximately 0.2 μm, and the other electrode (n-side electrode) 10of Au—Ge/Ni/Au or similar is formed on the entire rear surface of thesemiconductor substrate 1.

A mask is then formed through photolithographic techniques so as tocover only the surface of light emitting unit portions A, the electrodepad portion B and the connecting portions C, and the exposed currentdiffusing electrode 8 is etched by using an etching solution of iodineand potassium iodide and the semiconductor laminating portion 12 isetched by a liquid in which hydrochloric acid and water is mixed at aratio of 1:1 to 2:1 (wherein HCl is 47 wt %) at room temperature forapproximately 3 minutes (at a rate of 6 μm/min) so as to reach thesemiconductor substrate 1. Thereafter, dicing is performed such that thesize of the chip becomes, for instance, 330 μm by 330 μm to thus obtainthe light emitting device chip as illustrated in FIG. 1.

The present invention is characterized in that the light is not emittedat a portion which the light is shielded by the electrode by separatingthe electrode pad portion from the light emitting unit portions and bypreventing current from flowing to the light emitting layer formingportion of the electrode pad portions to make them nonluminous, and inthat light emitted at the light emitting layer forming portion can beeffectively extracted to outside of the semiconductor layers from theside walls by separating the light emitting layer forming portions intoa plurality of light emitting unit portions without successive layers onthe entire chip surface. The ratio of light that can be used uponextraction to the exterior with respect to the same amount of input(overall light emitting efficiency) could be remarkably improved, and animprovement by 120% in luminance with respect to the same mount of inputcould be achieved when compared to a luminance of a LED of conventionalstructure.

While the light emitting layer forming portion of the above-describedexample was of double hetero structure in which a non-doped active layeris sandwiched between n-type and p-type clad layers having a larger bandgap than that of the active layer, it is alternatively possible toemploy a pn junction structure in which the p-type layer and the n-typelayer are directly joined. The conductivity of the semiconductorsubstrate side may be of p-type and the conductivity of theabove-described respective semiconductor layers opposite thereto.

According to the present invention, since current injection is performedin an extremely effective manner, emitted light may be effectivelyextracted without loss and remarkably large optical outputs may beobtained with respect to the same amount of power input.

Although preferred examples have been described in some detail it is tobe understood that certain changes can be made by those skilled in theart without departing from the spirit and scope of the invention asdefined by the appended claims.

1-12. (canceled)
 13. A semiconductor light emitting device comprising: asubstrate; a semiconductor laminating portion formed on said substrate,said semiconductor laminating portion including a light emitting layerforming portion having at least an n-type layer and a p-type layer; acurrent diffusing electrode formed on said semiconductor laminatingportion, said current diffusing electrode exhibiting translucency andelectric conductivity; and a bonding electrode formed on a part of saidcurrent diffusing electrode; wherein said current diffusing electrode ispatterned so as to leave an electrode pad portion on which said bondingelectrode is provided, a plurality of light emitting unit portions, saidsemiconductor laminating portion under each of which emits a light, andconnecting portions for connecting between said electrode pad portionand said light emitting unit portions or between two of said lightemitting unit portions.
 14. The semiconductor light emitting device ofclaim 13, wherein a part of said semiconductor laminated portion whichis exposed by patterning said current diffusing electrode, is etched.15. The semiconductor light emitting device of claim 13, wherein a widthof each of said connecting portions is shorter than a size of a planarshape of one of said light emitting unit portions.
 16. The semiconductorlight emitting device of claim 15, wherein when a planar shape of one ofsaid light emitting unit portions is circular, the size of the planarshape is defined as a diameter of the circular shape.
 17. Thesemiconductor light emitting device of claim 15, wherein when a planarshape of one of said light emitting unit portions is rectangular orelliptical, the size of the planar shape is defined as a length of ashorter side or a shorter diameter thereof.
 18. The semiconductor lightemitting device of claim 15, wherein the width of said current diffusingelectrode of each of said connecting portions is 5 to 20 μm.
 19. Thesemiconductor light emitting device of claim 16, wherein the diameter ofthe circular shape is not more than six times a thickness of saidsemiconductor laminating portion.
 20. The semiconductor light emittingdevice of claim 19, wherein a thickness of said semiconductor laminatingportion is approximately 3 to 10 μm and the diameter of each of saidlight emitting unit portions is approximately 10 to 50 μm.
 21. Thesemiconductor light emitting device of claim 17, wherein a length of alonger side or a longer diameter is not more than six times a thicknessof said semiconductor laminating portion.
 22. The semiconductor lightemitting device of claim 13, wherein a distance between two adjoiningones of said light emitting unit portions is not less than twice athickness of said semiconductor laminating portion.
 23. Thesemiconductor light emitting device of claim 13, wherein said lightemitting layer forming portion is formed by a double hetero structurewhich sandwiches an active layer between a first clad layer and a secondclad layer, and further comprises a window layer which is interposedbetween said current diffusing electrode and said first clad layer whichis provided on said current diffusing electrode side of said lightemitting layer forming portion.
 24. The semiconductor light emittingdevice of claim 13, further comprising a reflecting layer provided onsaid substrate or on one layer above said substrate, in whichsemiconductor layers of different refractive indices are alternatelylaminated, each of said semiconductor layers having a thickness ofλ/(4n), wherein λ indicates a light emitting wavelength and n indicatesa refractive index of the semiconductor layer.
 25. The semiconductorlight emitting device of claim 13, further comprising a buffer layerwhich is provided between said substrate and said semiconductorlaminating portion to ease lattice mismatching therebetween.
 26. Thesemiconductor light emitting device of claim 13, wherein a currentblocking layer is formed on one layer between said current diffusingelectrode and said substrate in said electrode pad portion, so that saidlight emitting layer forming portion of said electrode pad portion isrendered nonluminous.
 27. The semiconductor light emitting device ofclaim 26, wherein said current blocking layer is anelectrically-insulating layer, or a semiconductor layer that hasdifferent conductivity from that of semiconductor layers adjoining saidcurrent blocking layer.
 28. The semiconductor light emitting device ofclaim 13, further comprising a current blocking layer formed on onelayer between said current diffusing electrode and said substrate insaid connecting portions, so that said light emitting layer formingportion of said connecting portions is rendered nonluminous.
 29. Thesemiconductor light emitting device of claim 13, wherein said substrateis an insulating substrate.